The objectives of this proposed research are to demonstrate the functional significance of progesteronic and estrogenic influences on gastrointestinal motor activity. In vivo steroidal administration, with subsequent in vitro assessment of regional tissue motor function under the influence of either hormone and both hormones will be made. The hormonal blood concentrations will be correlated with tissue function to provide a physiological evaluation of the hormonal influences. Pharmacological manipulations will be made to gain insight into hormonal mechanisms of action.